Thermal fatigue cracking, commonly referred to as fire cracking, is one of the most frequent degradation mechanisms encountered in heavy section steel mill rolls during hot rolling operations. Under intense cyclic heating from the hot steel sections and rapid cooling via water headers, the roll working layer expands and contracts alternatively, creating massive thermal stresses that eventually manifest as a network of surface cracks.
Key Metallurgical Factors
The depth and propagation speed of these cracks depend heavily on the roll’s microstructure and core material composition. For instance, Indefinite Chill Double Poured (ICDP) rolls leverage a specific flake graphite structure inside their working layer to absorb thermal shocks and delay crack networks from penetrating deep into the core.